Measuring Degradation Rates without Irradiance Data

A method to report photovoltaic (PV) system degradation rates without using irradiance data is demonstrated. First, a set of relative degradation rates are determined by comparing daily AC final yields from a group of PV systems relative to the average final yield of all the PV systems. Then, the difference between relative and absolute degradation rates is found using a Bayesian statistical analysis. This approach is verified by comparing to methods that utilize irradiance data.